Electric motor pump control incorporating pump element position information

ABSTRACT

A method and a system for controlling an electric motor of a pump to counter act pressure pulsations generated by at least one pump element and to reduce noise, vibration, and harshness generated by the pump. The positions of at least one pump element of the pump and a shaft of the electric motor are determined. A pump stroke position is determined from the position of the pump element relative to the position of the shaft of the electric motor. The power sent to the electric motor is controlled according to the pump stroke position.

FIELD

The invention relates to methods and systems for providing improved (orreduced) noise, vibration, and harshness (“NVH”) in the control of anelectric motor of a hydraulic pump. More particularly, embodiments ofthe invention relate to method and a system for control of an electricmotor driving a pump using information about the pump element positionto control the power of the motor in order to reduce the NVH generatedby the pump.

BACKGROUND

Generally, systems that include radial hydraulic pumps driven by anelectric motor are known in the industry. Examples of these hydraulicsystems include the Electronic Stability Program (“ESP®”) by RobertBosch and more particularly the ESP® premium system, which is based on aconventional hydraulic braking system (although it can perform thefunctions of an electro-mechanical braking system). The ESP® premiumsystem uses a hydraulic pump that has six pistons moved by an eccentriccam rotated by an electric motor. Other known hydraulic pumps systemsinclude fewer pistons (two or three, for example).

A common characteristic for systems that include a hydraulic pump drivenby an electric motor is that the pumping action generates pressurepulsations that create noise and vibration in the system. Depending onthe number of pistons and the speed of the electric motor, the level ofnoise and vibrations varies from system to system.

SUMMARY

A variety of methods exist that help to reduce different types of NVH.For example, to help reduce vibration in an engine (e.g., V-twinmotorcycle engine), a counterbalance effect method is applied. In orderto minimize the engine's vibration, a mass is used to balance out theunevenly balanced engine and to bring the engine into equipoise (theweights or forces in the engine offset one another). Other methods forreducing noise are disclosed in, for example, noise-cancelingheadphones. However, the previously disclosed methods for reducing NVHdo not propose reducing the noise and vibrations in a hydraulic pump byregulating the power of the electric motor of the pump based on theposition of the pump element.

Thus, there is a need for an improved method and a system forcontrolling and reducing the NVH produced by a hydraulic pump systemdriven by an electric motor. Embodiments of the invention control andreduce the NVH of an electric motor of a hydraulic pump by usinginformation about the pump element position relative to the pump strokeand manipulating or controlling the power of the electric motor based onthe pump stroke position. Embodiments are applicable to both, brushedand brushless direct-current (“DC”) motors.

The invention provides a method for controlling an electric motor of apump to counter act pressure pulsations generated by at least one pumpelement and to reduce noise, vibration, and harshness generated by thepump. The method determines a position of at least one pump element ofthe pump and a position of the shaft of the electric motor. Further, apump stroke position is determined from the position of the pump elementrelative to the position of the shaft of the electric motor. The powersent to the electric motor is controlled according to the pump strokeposition.

The invention also provides a system for controlling an electric motorof a pump to reduce noise, vibration, and harshness generated by leastone pump element of the pump. The system includes a controller, and aplurality of sensors connected to the controller. Each of the sensors isconfigured to transmit information to the controller, and a networkconnects the sensors to the controller. The controller determines aposition of a pump element and a position of a shaft of the electricmotor. Further, the controller determines a pump stroke position fromthe position of the pump element relative to the position of the shaftof the electric motor. Finally, the controller controls a power sent tothe electric motor according to the pump stroke position. Other aspectsof the invention will become apparent by consideration of the detaileddescription and accompanying drawings.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an electric motor of a pump and componentsfor controlling the electric motor using information about the pumpelement position.

FIG. 2 is a schematic illustration of a system for controlling anelectric motor of a pump.

FIG. 3 is a block diagram of a pump electric motor control module.

FIG. 4 is a graph depicting a target power profile used by the systemfor controlling an electric motor of a pump shown in FIG. 1, where thetarget power is in phase with the pump element position.

FIG. 5 is a graph depicting a target power profile used by the systemfor controlling an electric motor of a pump shown in FIG. 1, where thetarget power is out of phase with the pump element position.

FIG. 6 is a graph depicting a target power profile used by the systemfor controlling an electric motor of a pump shown in FIG. 1, where thetarget power frequency is two times the pump element stroke.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

As should be apparent to one of ordinary skill in the art, the systemsshown in the figures are models of what actual systems might be like. Itshould also be noted that a plurality of hardware and software baseddevices, as well as a plurality of different structural components, maybe utilized to implement the invention. Many of the modules and logicalstructures described are capable of being implemented in softwareexecuted by a microprocessor or a similar device or being implemented inhardware using a variety of components. As described in subsequentparagraphs, the specific configurations illustrated in the drawings areintended to exemplify embodiments of the invention and other alternativeconfigurations are possible. Furthermore, throughout the specificationcapitalized terms are used. Such terms are used to conform to commonpractices and to help correlate the description with the codingexamples, equations, and/or drawings. However, no specific meaning isimplied or should be inferred simply due to the use of capitalization.Thus, the claims should not be limited to the specific examples orterminology provided.

FIG. 1 illustrates one embodiment of a system for control of an electricmotor of a pump using information about the pump element position (e.g.,a piston). The pump electric motor control system 12 generally includesa hydraulic pump 10 and position sensors 20 (not shown) that are locatedon or around a shaft 17 of the electric motor 18 of the pump 10.Further, the pump electric motor control system 12 includes a controller24 (FIG. 2) and a power control device 25 (FIG. 3) that manipulates thepower sent to the electric motor 18. In one of the embodiments, thesystem 12 uses several position sensors. However, as explained ingreater detail below, the system 12 can also operate with one sensor 20or without any sensors at all. In addition, the arrangement and theposition of the sensors 20 of the system 12 can vary depending on thedifferent embodiments of the system and the type of sensors used inthose embodiments. Generally, the sensors 20 are directly connected tothe controller 25. In an embodiment, the sensors are connected to anetwork, such as a controller area network (“CAN”) bus 22, which isconnected to the controller 24.

As further show in FIG. 1, the hydraulic pump 10 includes an electricmotor 18, an eccentric cam (or, simple “eccentric”) 14, a rotating shaft17, and a number of pump elements (pistons) 16. The pump 10 isoperatively connected to and driven by the motor 18. In one embodiment,the system 12 includes a pump 10 with three pump pistons 16. Inalternative embodiments, the system 12 can include pumps with differentnumber of pump pistons (two, four, six, etc.). The pump elements 16 arelocated near the motor 18 and are pushed up and down by the eccentric14, which is rotated by the shaft 17 of the motor 18. Several positionsensors 20 (not shown) are operatively coupled to the shaft 17 of themotor 18 and are connected to the controller 24.

In the embodiment shown in FIGS. 1-3, the system 12 determines theposition of the pump element 16 (as a function of time) relative to theangular position of the shaft 17 (i.e., relative to the pump stroke) inorder to control the power sent to the electric motor 18. The rotationof the shaft 17 of the electric motor 18 has a fixed relationship to themovement of the pump element 16. Thus, by controlling the power of theelectric motor 18 in relation to this pump stroke position, the system12 affects (i.e. reduces) the noise and vibration levels created by thepump 10. In other words, the system 12 determines whether the pumpelement 16 is pumping fluid or not in a particular moment so it canpulse the motor power or otherwise control it based on the pump elementposition.

As described in greater detail below, the position of the pump element16 and the shaft 17 can be determined directly by using a positionsensor or a plurality of position sensors, or indirectly by monitoringand measuring the motor voltage. After the position of the pump elementis determined, the system selects a “target power profile” from a tablewith various target power profiles stored in the memory of thecontroller in order to regulate the power sent to the motor 18. Thistarget power is based on the previously determined pump elementposition. The system 12 uses a power control device 25 (an amplifier, atransducer, or another type of transformation device) to manipulate theelectrical energy sent to the pump motor 18 to affect (i.e., counteract) the pressure pulsations generated by the stroke of thereciprocating pump element 16.

In one embodiment of the invention, the system 12 obtains informationabout the position of the pump element directly by using severalposition sensors. These position sensors 20 are placed on or around theshaft 17 of the electric motor 18. The controller 24 receives theappropriate sensor signals and inputs from the position sensors 20 thatindicate the position of the pump elements 16 and the angular positionof the shaft 17. For example, direct position measurement could beaccomplished by using Hall effect sensors or rotary encoders. Otherposition sensors can also be used.

One embodiment of the invention utilizes an advanced (and moreexpensive) sensor array having a large number of position sensors (Halleffect sensors), which are positioned on or around the rotating shaft17. By using an advanced sensor array, the system 12 obtains moreprecise position information of the pump element and the shaft.

In an alternative embodiment, where the system 12 is builtinexpensively, only a single position sensor is used to determine thepump stroke position. In that case, the system receives positioninformation for only part of the rotation of the shaft 17 (for examplethe system can receive a pulse for 5 degrees on every rotation). Thesystem 12 then estimates the position of the shaft 17 for the rest ofthe rotation based on various additional factors—the rpm of the electricmotor, the sum of torques acting on the motor, and the overall pressurethat the pump 10 is working against. The system combines these factorswith the initial sensor measurement in order to estimate the futureposition of the pump element and subsequently verifies whether thisposition is correct.

In another alternative embodiment, the system 12 uses electricalmonitoring to indirectly determine the position of the pump element 16in relation to the pump stroke. In this alternative embodiment, thesystem 12 determines the position of the pump elements 16 and the shaft17 without any position sensors 20. For example, in a brushed DC motor,the system 12 measures the electrical signal of the motor wire as thecommunicator switches from one winding to another in order to determinethe position of the shaft 17 and the pump element 16. A similar methodfor indirectly determining the position of the electric motor and thepump element is described in EP 2096749 A1. The system 12 can alsoindirectly determine the position of the electric motor and the pumpelements in a brushless DC motor. Thus, the position of the pump element16 and the shaft 17 can be also determined indirectly without the use ofposition sensors. Although it is possible to implement, indirect or“sensorless” determination of the pump element position is not preferredfor electronic stability control systems because the electric motorstarts and stops frequently and the starting and stopping makes itdifficult to keep track of the position of the motor elements.

FIG. 2 schematically illustrates the functionality of the pump electricmotor control system 12 of FIG. 1 in greater detail. As shown in FIG. 2,the control system 12 includes the controller 24 and one or more sensors20. The controller 24 obtains sensor readings directly from one or moreof the sensors 20. In some circumstances, especially when the systemuses less sensors to determine the position of the pump element 16,compensated sensor readings are used by the controller 24, rather thanraw data. For example, in some circumstances, the controller 24compensates one or more of the sensor readings by applying an offset.Offsets are used to compensate for sensor aging, fouling, and othersignal corruption that may occur.

In many implementations, controller 24 includes a processor such as amicrocontroller or microprocessor, associated electronic circuitry suchas input/output circuitry, various programmed modules, and one or morememory components.

As shown in FIG. 2, the controller 24 includes an input/output interface40, an electronic processing unit (“EPU”) 42, and one or more memorymodules, such as a random access memory (“RAM”) 44 and read-only memory(“ROM”) 45. The input/output interface 40 transmits and/or receivesinformation, including sensor readings from the sensors 20. Thecontroller 24 also includes a pump electric motor control (“PEMC”)module 50 that is executed by the EPU 42. The PEMC module 50 isarchitected to determine the position of the shaft 17 and the pumpelement 16 relative to the pump stroke and controls the power of theelectric motor 18 in relation to the determined control position.

The EPU 42 receives information (such as sensor readings) from theinput/output interface 40 and processes the information by executing oneor more applications or modules. The applications or modules are storedin memory, such as ROM 45. The EPU 42 stores information (e.g.,information received from the sensors 20, or information generated byapplications or modules executed by the EPU 42) to the RAM 44. Forexample, the RAM 44 can store the various positions of the shaft 17 andthe pump elements 16 that are detected by the sensor 20. In addition,the RAM 44 can also receive and store data from the PEMC module 50 orother components of the system 12. The RAM 44 also stores a table withvarious target power profiles that is accessed by the PEMC module 50 inorder to select a target control power that manipulates the electricmotor 18. In the embodiment shown in FIG. 2, RAM is used. In otherembodiments, other memory devices can be also implemented.

FIG. 3 illustrates the operation of pump electric motor control (“PEMC”)module 50 in greater detail. In the particular embodiment illustrated,the PEMC module 50 is configured to determine the position (stroke) ofthe pump element 16, which has a set relationship with the electricmotor 18 as the motor shaft 17 rotates, and to control the power of theelectric motor 18 in relation to the pump stroke position. The PEMCmodule 50 receives sensor signals from the sensors 20 (or in thealternative embodiment a single sensor) through the input/outputinterface 40 and based on these signals determines the position of thepump element 16. The PEMC module 50 determines the pump strokeposition—this is the position of the pump element 16 relative to thepump stroke (i.e., the motion of the pump element as the pump is movingor whether the pump element is pumping fluid or not). The pump strokeposition is determined based on the position of the electric motor 18(using the motor shaft position) relative to the position of the pumpelement 16. The PEMC module 50 then selects a target control power fromthe table with target power profiles according to the determined pumpstroke position.

The PEMC module 50 uses the power control device 25 to manipulate thepower sent to the electric motor 18 in accordance with the selectedtarget control power. Controlling the power sent to the motor 18includes voltage control (e.g., pulse width modulation control) orcurrent control (e.g., by specific hardware) depending on theimplementation of the system. By regulating the power of the electricmotor 18 in relation to the stroke of the pump element 16, the PEMCmodule 50 helps to affect (i.e. reduce) noise, vibration, and harshnessgenerated by the pump 10. In one embodiment, the power control device 25is a metal-oxide-semiconductor, field-effect transistor (MOSFET) controldevice. In alternative embodiments, the power control device 25 can bean amplifier, transducer, or other control device.

In order to timely change the power of the motor 18 based on theposition of the pump element 16, the system 12 executes the PEMC module50 at a high rate in order to keep up with the repeating pressure pulsecreated by the pump elements 16. For example, in a pump with two pumpelements, the motor 18 operates at 5000 rpm (equal to 83.3 Hz) andproduces 167 pulses per second (5000 rpm times two). The system 12executes the PEMC module 50 approximately 10 times faster than anindividual pump element cycle. Thus, in this case, the PEMC module 50 isexecuted for approximately every (1 sec/167 pulses)*(0.1)=0.6 ms. Duringthe PEMC module execution time (0.6 ms=0.0006 s), the system 12determines the pump stroke position, selects a target control power fromthe table with target power profiles, and regulates the voltage of themotor 18.

The operation of the pump electric motor control (“PEMC”) module 50 isfurther illustrated in FIGS. 4-6. In particular, FIGS. 4-6 representseveral target power profiles that are stored in the RAM 44 and are usedby the PEMC module 50 in order to select a target control power tocontrol the electric motor 18. Additional target power profiles can becreated and used in various embodiments of the invention. The waveformgraphs in FIGS. 4-6 represent embodiments of the invention where thepump 10 includes three pump elements or pistons 16 (as shown in FIG. 1).In alternative embodiments of the invention, a different number of pumpelements can be used. The waves at the lower portion of FIGS. 4-6represent the movement/stroke of the pump elements 16. In general, thesepump elements 16 generate a pressure pulse every 120 degrees. Themeasurements on the left hand side of the graphs represent the pumpelement position relative to the pump stroke (in mm). The measurementson the right hand side of the graphs represent the level of the targetcontrol power (in amperes). The measurements on the bottom of the graphrepresent the angular position of the shaft 17 (in degrees). The targetcontrol power illustrated in the upper portion of the graph is afunction of the shaft position in relation to the pump element position.For example, if the pump element is at 240 degrees position the targetpower is 8.5 amperes.

FIG. 4 represents one target power profile that is used by the system12. After the system 12 determines the pump stroke position based on thepump element position and the shaft angular position, the system 12selects a target power profile from the table stored in RAM 44. FIG. 4shows a situation where the target power is in phase with the pumpelement position. In other words, the target power will increase whenthe pump is moving and will decrease when the pump is not. Thus, system12 provides most power to the electric motor 18 when the pump is doingmost of the work.

FIG. 5 illustrates a second target power profile that is used by thesystem 12. In FIG. 5, the target power is out of phase with the pumpelement position. In other words, the target power will be less when thepump element is moving and the target power will go up when the pump isnot moving. Thus, the target power creates an oscillation wave that isexactly out of phase with the pump noise wave and the two waves willinteract. In the right condition, these two opposite phase oscillationscan combine with the result being a smaller wave.

FIG. 6 shows a third target power profile that is used by the system 12.The target power profile illustrated in FIG. 6 shows that when thesystem 12 determines the pump element position, the system 12 can adjustthe target power (at an increased or decreased level) in order to obtainthe best overall performance of the pump 10. In this case, the targetpower is two times the pump element stroke and is in phase with the pumpelement position. The system manipulates the target power with respectto the pump stroke in such a manner in order to improve NVH of the pump.

Various features and advantages of the invention are set forth in thefollowing claims.

1. A method of controlling an electric motor of a pump to counter actpressure pulsations generated by at least one pump element and to reducenoise, vibration, and harshness generated by the pump, the methodcomprising: determining a position of at least one pump element of thepump; determining a position of a shaft of the electric motor;determining a pump stroke position from the position of the at least onepump element relative to the position of the shaft of the electricmotor; and controlling a power sent to the electric motor according tothe pump stroke position.
 2. The method according to claim 1, furthercomprising controlling the power sent to the electric motor by using atarget control power.
 3. The method according to claim 1, furthercomprising directly determining the position of the pump element and theposition of the shaft of the electric motor.
 4. The method according toclaim 1, further comprising indirectly determining the position of thepump element and the position of the shaft of the electric motor.
 5. Themethod according to claim 3, further comprising directly determining theposition of the pump element and the position of the shaft of theelectric motor by using position sensors.
 6. The method according toclaim 1, further comprising selecting a target power profile from atable with various target power profiles stored in a memory of acontroller.
 7. The method according to claim 6, further comprisingselecting the target control power from the target power profiles, wherethe target control power is a function of the position of the shaftposition and the position of the pump element.
 8. The method accordingto claim 1, further comprising determining the pump stroke position byexecuting a pump electric motor control (“PEMC”) module.
 9. The methodaccording to claim 8, further comprising executing the pump electricmotor control (“PEMC”) module at a speed faster than an individual pumpelement cycle.
 10. The method according to claim 7, further comprisingselecting a target control power that is in phase with the position ofthe pump element.
 11. The method according to claim 1, whereincontrolling the power sent to the electric motor includes a voltagecontrol or a current control.
 12. A system for controlling an electricmotor of a pump to reduce noise, vibration, and harshness generated byleast one pump element of the pump, the system comprising: a controller;a plurality of sensors connected to the controller, each of the sensorsconfigured to transmit information to the controller; and a networkconnecting the sensors to the controller; wherein the controller isprogrammed to: (1) determine a position of a pump element and a positionof a shaft of the electric motor, (2) determine a pump stroke positionfrom the position of the pump element relative to the position of theshaft of the electric motor, and (3) control a power sent to theelectric motor according to the pump stroke position.
 13. The system ofclaim 12, wherein the controller further comprises a pump electric motorcontrol (“PEMC”) module that receives sensor signals from the sensorsand determines the pump stroke position.
 14. The system of claim 12,wherein the controller is programmed to select a target power profilefrom a table with various target power profiles stored in a memory ofthe controller.
 15. The system of claim 14, wherein the controller isprogrammed to select a target control power from the target powerprofiles, where the target control power is determined based on theposition of the shaft relative to the position of the pump element. 16.The system of claim 15, wherein the controller is programmed to select atarget control power that is in phase with the position of the pumpelement.
 17. The system of claim 15, wherein the controller isprogrammed to select a target control power that is out of phase withthe position of the pump element.
 18. The system of claim 15, whereinthe controller is programmed to select a target control power operatingat any increased or decreased level in order to improve the overallperformance of the pump.
 19. The system of claim 12, wherein thecontroller is further programmed to control the power sent to theelectric motor by using a power control device.
 20. The system of claim12, wherein controller is further programmed to control the power sentto the electric motor by a voltage control or a current control.